The manufacturing operations do not call for detailed notice here. The processes of rolling, casting, punching, chasing, hammering, stamping, soldering, riveting, and burnishing, all come into requisition in the manufacture of a piece of plate of any considerable size or elabo ration of design.
The proportion, however, of articles of plate mado of real gold or silver throughout is very small compared with that of articles in which the surface only is of precious metal, laid upon a metal of cheaper character. By pressure between steel rollers, a thin layer of gold or silver may be made to adhere to a thicker layer of some cheaper metal, and of the compound layer thus produced numerous articles may be made. A clam of goods called Skejlield plate used to be very largely manufactured of such compounds. The product has been consider ably Improved by the adoption of a white metal for the ground or foundation. This white metal is usually a compound of nickel with certain other metals; and the colour bears a, sufficiently close resem blance to that of silver to render it advantageous iu since it will not show a coppery or brassy tint when the silver is worn away. Articles of real silver plate are sometimes coated with real gold on one side, or in certain parts, and these obtain the designation of silrer-gilt The whole trade, however, has undergone a revolution within the last few years, by the introduction of the process of electro-metallurgy, oI electro-plating. By this process a work of art may be made wholly of
gold or silver, or of a film of those metals on a ground of less value, b3 deposition from certain chemical liquids through the agency of z galvanic battery. The processes are explained under ELECTRO METALLURGY. The annexed wood-cut will illustrate the remarkable series of operations (as described in that article) by which the better kinds of electro-plate are produced : a is a model for a silver cup, formed of wax or composition, and sculptured with an artistic design on the outer surface ; b is one half of au elastic mould, made of caoutchoue and other substances, and obtained by casting from the model, with the device inside instead of out ; e is a copper cup obtained by electro-deposition upon the interior of the mould, and afterwards detached from it ; d is the finished cup, with an electro-silver surface upon an electro-copper ground, and a handle attached. If possible, white metal is used instead of copper as a basis.
There are many curious modes of coating plates of metal with thin films of other metal, wholly distinct from those in which gold and silver are employed. Most of them, however, bear analogy to TINNING or TIN-PLATING, and will be briefly adverted to in that article.